1. Field of the Invention
The present invention relates to a vehicle driving force control device for controlling a driving force so as to appropriately maintain grip forces of vehicle wheels.
2. Description of the Related Art
In recent years, various types of vehicle driving force control devices that inhibit an excessive driving force to maintain grip forces of vehicle wheels have been developed and put to practical use. For example, Japanese Unexamined Patent Application Publication No. 10-310042 discloses a technology in which an estimate value of a friction-circle radius of each wheel is determined, and a resultant force of a lateral force and a longitudinal force generated on each wheel estimated from the driving condition of the vehicle is adjusted within a range not exceeding the estimate value of the friction-circle radius.
However, the technology disclosed in Japanese Unexamined Patent Application Publication No. 10-310042 is such that it simply tries to keep a currently generated resultant force of a lateral force and a longitudinal force within the estimate value of the friction-circle radius.
For this reason, this technology is disadvantageous in that it cannot respond effectively to a driving force that may presumably be generated in the future. Therefore, with this technology, for example, if the vehicle is currently spinning, a proper response to the situation is possible, whereas if the vehicle is in a plowing condition, a proper response to the situation is not possible.
In addition, if the grip forces of the wheels are precisely applied and the engine output is reduced, a drawback may possibly occur during uphill driving on, for example, a slope.